Shadowsocks port setup

Hi, I’m on B1300 following this guide to set up SS server, Shadowsocks - GL.iNet Docs
if following the guide and using port 443, it doesn’t work, but changing it to a different port works, any idea why it doesn’t work on port 443?

Some ISP’s block port 443 (or 80) if they don’t want people running servers at home. If you get Shadowsocks to work in a different port just go with that…